1. Description of the Problem
Stabilization of airships has normally been accomplished by the use of tail fins near the stern, to which are attached movable control surfaces of a size sufficient to maintain or change the angle of incidence of the airship hull relative to airflow in forward flight. Due to their necessary large size, clearance between tail fins and the ground or other obstacles has been a problem. While small buffer wheels have sometimes been used on the bottom of tail fins, but considering the fins delicate nature in the interest of light weight, they have not been designed to withstand the high loads of ground strikes. They have also been damaged by excessive wind gusts in flight. Tail fins designed to carry high loads into the airship structure subject it to abrupt and uncomfortable movement, as well as necessitating a strong, and thus heavy, structure.
When near the ground as in takeoff, landing, loading, or docking operations airships are handled by a numerous ground crew handling ropes attached to the airship. Part of their job is to avoid tail strikes to the ground. However, as with ropes they can only pull downward or sideward their effect is useless when an odd wind gust forces the tail downward. Thus tail strikes to the ground cannot be avoided altogether, and continue to occur. This has had a part in lowering the public image of airships as practical aircraft and thus their economic viability, restricting their use.
As larger airships are again being built, the use of semi rigid and rigid construction will see a revival, and the problem of limiting serious damage to the tail structures and their attachment to the rigid framing will again be a problem.
As one of the major components of an airship, the weight of engines subject the airship structures to concentrated inertia loads during fast maneuvers, gust encounters, and ground handling. Similar to excessive loads to the tail fins, such loads can damage the airship structure or require it to be built unduly heavy to withstand them.
When engines and landing gear are mounted near the middle length of the airship, the concentration of mass leads to reduced inertial resistance to pitching and yawing and a more unstable airship. While highly desirable for passenger comfort and stability, and sometimes proposed, the location of engines in solidly mounted airship tails will subject the airship structure to excessive inertial bending loads in gust encounters or hard landings.
The exposed landing gear of airships cause considerable drag and risk of catching on obstacles. To allow a vertical travel to dissipate loads, they add unduly to the height of the airship, making maintenance, hangar clearance, and comfortable passenger entry and exit a problem.
Another important consideration is safely and accurately locating the airship for movement in and out of hangars and near obstacles, without subjecting the airship structure to excessive or unduly concentrated loadings. While a nose mooring attachment provides a secure, and often resilient, attachment point forward when used with a mobile mooring mast, airships have lacked an effective means of resiliently locating the rear of the airship relative to the ground or obstacles. Rear handling lines need a complex attachment system and add to aerodynamic drag, while providing little protection against rolling or downward movement at the tail. This has severely limited the wind conditions in which airships can be safely maneuvered on the ground and maximizes the necessary side clearances for safe hangaring, necessitating oversize hangars and, again, large ground crews.